Methods of Extraction for Essential Oils
The different methods of extracting essential oils
There are three principal methods of extracting essential oils from
aromatic plants. These are: expression processes; distillation
processes; and extraction using volatile solvents.
Expression
This method is only used for citrus fruit. The essential oils in citrus
fruits arc situated close to the surface of the peel and are easily
obtained by squeezing and scarification (finely puncturing the peel).
Expression methods include the sponge method and machine abrasion, the
former being more traditional and producing a very pure essential oil.
You can experiment at home with hand expression and produce small
quantities of your own citrus essential oils. Wash and dry the fruit and
cut off segments of peel. Using your fingers, squeeze the peel over a
small bowl to collect the drops of essential oil. Store them in a small,
dark glass bottle with a dropper insert, and use them as you would any
other citrus oil.
Distillation
Distillation processes involve heating the plant material until a vapor
is formed, then cooling the vapor until it becomes liquid. In water
distillation, the plant material is covered in water and heated in a
vacuum-sealed container. This method is slower and sometimes inferior to
steam-distillation, because certain delicate components of essential
oils are damaged by exposure to heat. The more efficient
steam-distillation uses steam under pressure to swiftly extract the
essential oil.
Solvent extraction
For the most delicate plant material, such as flowers, and for those
containing only a small amount of essential oil, solvent extraction
processes are used. The main advantage is that this method is gentle,
but the resulting essential oils include non-volatile waxes and plant
dyes, as well as the essential oil itself. Nonetheless, these essential
oils are considered by many authorities to be fine for use in
aromatherapy. The main solvents used in modern production are volatile
hydrocarbons (such as hexane).
A recent innovation is a process called hypercritical carbon dioxide.
This is reputed by some authorities to produce essential oils of very
high quality and purity, though others are critical of oils produced in
this way. The process requires very expensive equipment, so essential
oils produced in this manner are difficult to obtain and expensive.

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